The proposed project involves a collaboration with the Gorgas Memorial Laboratory in Panama City, Panama. The Gorgas Memorial Laboratory will supply support to this project by assisting in collecting samples on patients with various malignancies suspected to be linked to HTLV and from corresponding normal populations. Studies will be undertaken to determine the distribution of HTLV infection in Panama to see whether virus clusters occur in regions of the County and within households. In addition, serum will be collected prospectively on various other high-risk populations such as close family members of cases. Finally, case-control strategies will be developed where appropriate to define the risk factors associated with HTLV infection and leukemia. The epidemiologic guidance for this project will come from the Principal Investigator and the Environmental Epidemiology Branch of the National Cancer Institute. Personnel to implement the epidemiologic components of this project will be supplied by the proposed contractor.